Aye, the seals and swcc's use a 33 foot boat for inland and coastal work. Has two 7.62 mm chain guns, 2 40mm grenade launchers, and a .50 cal machine gun. Capable of around 80 knots, and a 180 degree turn in under two boat lengths.

Are you looking for a modern PT boat or a craft designed to carry special operations forces.

Remember the PT boats of WWI were ~80ft in length and carried four torpedoes, capable of sinking or at least mission killing ships much larger than the PT boat itself. There is no equivalent in the modern USN. The closest was probably the PHM class.

There are MkVs in Naval Special Warfare. They are 85ft long, IIRC, and can carry several crew served weapons, .50cals, M240s/M60s, Mk19s that sort of thing. But their real purpose is to go in and deliver SEALs.